Earlier systems for generating data bases for computer-generated images and for Digital Radar Landmass images have been based on hand-modelling or on transformation of Defense Mapping Agency (DMA) digital data bases. In hand-modelling, data bases typically are designed on paper as objects composed of edges and faces, then transferred into a computer data base through a digitizing process or through the direct entry of coordinate data in numerical form.
A somewhat more sophisticated system of hand-modelling utilizes interactive graphics terminals on which objects can be designed with an electronic cursor, eliminating the use of paper drawings. In either case, however, the design process is relatively slow and consumes far more labor than can be afforded if very large areas are to be designed.
In the transformation system, digital data bases available from the Defence Mapping Agency are utilized to provide the raw information about the shape of the ground and certain other characteristics of an actual real scene. Typically, this information is available as a set of ground elevation values at the intersections of a grid, plug latitude-longitude coordinates of points on polygons representing the boundaries of respective features to be depicted.
This data is transformed through a lengthly computer process into the objects, faces, and vertices required to define computer-generated image and Digital Radar Landmass data base entities. However, Defense Mapping Agency data typically does not contain the density of information (by a factor of 100 or more) needed to portray detailed computer-generated images or scenes needed for training in flight near the ground, or detailed digital radar landmass scenes needed to train in the use of synthetic-aperture radar.